Tools used for picking up parts, such as semi-conductor chips and the like, can be made from simple tubes attached to a vacuum source. However, such pick-up tools for use with delicate objects, such as semi-conductor devices, could damage the object being picked up. Pick-up heads have been developed for such operations.
The pick-up heads urge an article against a projection by a vacuum-produced base on the aereodynamic paradox (Bernoulli's principle) between a dish-shaped article and the surface of a support facing an article. Since a projection or several projections engage an article outside of its center, it can be securely retained, such as during a treatment operation or even set into rotation.
Such pick-up heads, which can also be termed "grippers", can be incorporated as gripping units of robots and manipulators or nippers for various technological processes. Gripping tables of micro- and mini-centrifuges in microelectronics can use such technology. Such grippers can also be used for gripping and carrying liquids to hard to reach localities, such as in the case of performing electrochemical and chemical operations in manufacturing printed circuit cards, precision etching with subsequent removal of the etching products from working areas, automation means in producing lacquer coatings, in the food industry, optics, and photolithograthic processes.
Examples of such pick-up heads or grippers are disclosed in U.S. Pat. No. 5,169,196 to Safabakhsh, issued Feb. 8, 1992, and 5,492,566 to Sumnitsch, issued Feb. 29, 1996. Each of these prior art references disclose a pick-up tool or pick-up head including a housing having a disk disposed therein. The disk changes a fluid flow from a cylindrical flow to a planar flow by directing the cylindrical flow over a conical-shaped insert. The insert has a flat working surface exposed to the article being gripped thereby. Such devises have contact-vacuum principle of operation. This hinders gripping parts with uneven surfaces, parts with holes, as well as those coated with various liquids and other consistent materials. Also, such a vacuum can distort brittle or thin parts.
In view of the above, it is desirable to provide a gripper unit which reduces to a minimum the contact between the surface gripped and the area of the vacuum formation, to increase accuracy when establishing a line of demarcation between local areas and vacuum creation, as well as to increase efficiency, uniformity, and vacuum depth with minimum power conception. It is also advantageous to use liquid media as a energy carrier.